Cultivated forms of garden bean belong to the highly variable species Phaseolus vulgaris L. that is commonly grown for its seeds (beans) and fruits (pods), which are harvested together as an immature pod before the seeds have fully matured. This immature pod is known by many different common names, including green bean, string bean, snap bean, French bean, haricot bean, and filet bean. As a crop, garden bean is grown commercially wherever environmental conditions permit the production of an economically viable yield. Bean cultivars may be grouped by their growth habit into two groups. Bush or dwarf cultivars grow as erect bushes or short vines, do not require support, and are commonly grown on commercial farms. Pole, climbing, or running cultivars grow as long vines that climb supports, and are commonly grown in home vegetable gardens. The size of garden bean pods ranges from small to large, and from narrow, round French types to wide, flat Roma types. More recent developments in garden bean breeding have led to a wider array of fruit color. In addition to the standard green color, pods can be purple, red, yellow, or mottled. Garden beans are consumed fresh or cooked, and can be sold in fresh, frozen, dried, or canned form.
Phaseolus is a genus within the family Fabaceae, and consists of about 70 species. Fabaceae (or Leguminosae) is one of the largest land plant families, with an estimated 19,000 species, and contains multiple crop species including lentil, chickpea, soybean, bean, pea, peanut, and alfalfa. The leguminous plants of this family are characterized by their symbiosis with Rhizobium bacteria, which fix atmospheric nitrogen that is eventually released into the soil. Legumes are therefore often used to increase the nitrogen content of soil, and frequently grown either in rotation or concurrently with other crops. One example of this is found in indigenous North American agriculture, where beans are a member of the “Three Sisters” and are planted with squash and maize.
Phaseolus vulgaris L. is a highly variable species with a wide diversity of phenotypes. P. vulgaris L. is native to the Americas, and has a long history of cultivation dating from the second millennium BCE and spanning South and North America. There are three broad types of bean cultivars, namely dry bean, shelling bean, and green bean. Two separate domestication events from two genetically distinct wild populations in Middle America and the Andes resulted in two distinct gene pools among bean cultivars (Gepts, HortScience, 33:7, 1124-1130 (1998)). These two gene pools can be distinguished using phenotypic and genetic characteristics, and each provides qualities useful in developing new bean cultivars. Each gene pool has been used to develop different commercial seed classes; in the Andean gene pool, the Nueva Granada race includes kidney beans and green beans, while in the Middle America pool, the Mesoamerican race includes navy and black beans and the Durango race includes pinto beans.
Garden bean is an important and valuable crop. Thus, there is a continued need for new garden bean varieties. In particular, there is a need for improved garden bean varieties that are stable, high yielding, and agronomically sound.